Downscaling Effect on the Superconductivity of Pd₃Bi₂X₂ (X = S or Se) Nanoparticles Prepared by Microwave-Assisted Polyol Synthesis

Abstract

Pd3Bi2S2 and Pd3Bi2Se2 have been successfully prepared in the form of nanoparticles with diameters of ∼50 nm by microwave-assisted modified polyol synthesis at low temperatures. The composition and morphology of the samples have been studied by means of powder X-ray diffraction as well as electron microscopy methods, including X-ray intensity mapping on the nanoscale. Superconducting properties of the as-prepared samples have been characterized by electrical resistivity measurements down to low temperatures (∼0.2 K). Deviations from the bulk metallic behavior originating from the submicrometer nature of the samples were registered for both phases. A significant critical-field enhancement up to 1.4 T, i.e., 4 times higher than the value of the bulk material, has been revealed for Pd3Bi2Se2. At the same time, the critical temperature is suppressed to 0.7 K from the bulk value of ∼1 K. A superconducting transition at 0.4 K has been observed in nanocrystalline Pd3Bi2S2. Here, a zero-temperature upper critical field of ∼0.5 T has been estimated. Further, spark plasma-sintered Pd3Bi2S2 and Pd3Bi2Se2 samples have been investigated. Their superconducting properties are found to lie between those of the bulk and nanosized samples.

Weak Anti-localization in thin films of the Topological Semimetal Candidate Pd$_{3}$Bi$_{2}$S$_{2}$

“…The XRD pattern confirmed that our thin film crystallizes in the expected cubic crystal structure with space group I2 1 3. A Rietveld refinement of the XRD pattern gave the lattice parameters a = b = c = 8.47 Å, which are in agreement with values reported previously for bulk PBS [19][20][21]. Figure2(a-c) shows the atomic force microscope (AFM) topography image of PBS thin films.…”

“…21 We also observe a slope change in the sheet resistance close to 220 K seen in all films, which was not observed in bulk samples. [19][20][21] The origin of this slope change is not understood at present but we speculate that the connectivity between grains is changing with temperature, leading to a change in the conductivity of the films. To try to analyze how annealing affects the resistance of different films, we compare the residual resistivity ratio (RRR) and the residual resistivity R o in Table I.…”

“…A Rietveld refinement of the XRD pattern gave the lattice parameters a = b = c = 8.47 Å, which are in agreement with values reported previously for bulk PBS. [19][20][21] Figure 2(a-c) shows the atomic force microscope (AFM) topography image of PBS thin films. These images indicate the polycrystalline granular growth of the films.…”

“…18 In previous studies, the magnetotransport has been reported on polycrystalline, singlecrystalline, and nanoparticle samples of Pd 3 Bi 2 S 2 . [19][20][21] The magneto-transport study on single-crystal indeed revealed interesting features like a large non-saturating magneto-resistance, and presence of more than one type of charge carriers with very high mobility. 21 Reduction of system dimensionality from three dimen-sional (3D) to two dimensional (2D), is expected to lead to the emergence of several quantum phenomena at low temperatures, including weak localization (WL) or weak anti-localization (WAL), quantum interference (QI [22][23][24][25] , and universal conductance fluctuations (UCF).…”

Palladium Nanoparticles in Polyols: Synthesis, Catalytic Couplings, and Hydrogenations

“…Moreover, the microwave-assisted polyol methodology was applied in the preparation of nanosized ternary Pd 3 Bi 2 X 2 (X = S, Se) phases (ca. 50 nm), using EG as solvent; microwave irradiation favors the dissolution of reagents, in particular in this case, elemental selenium 113. 2.2.2.…”